四环己烷并卟啉的光谱性质及质子化反应常数的测定

Spectroscopic Determination of Protonation Reaction Constants of Tetrabutanoporphyrins

本文测定了5,10,15,20-四(4-甲苯基)四环己烷并卟啉(1)、5,10,15,20-四苯基四环己烷并卟啉(2)和5,10,15,20-四(4-氯苯基)四环己烷并卟啉(3)在二甲基亚砜(DMSO)中的紫外-可见光谱,与相应的无环己烷并取代基的卟啉相比,所测定化合物的光谱吸收峰红移了19~33nm。同时测定了这三个四环己烷并卟啉在三氟乙酸(TFA)-DMSO和氢氧化四丁基铵(TBAOH)-DMSO介质中的吸收光谱,并与化合物在纯DMSO溶剂中的光谱进行了比较。在含有TFA或TBAOH的溶液中,化合物的Soret吸收峰均发生红移,而Q吸收峰数目则相应减少,表明化合物与酸发生了质子化反应,与碱则发生了去质子化反应。采用微量光谱法测定了每种四环己烷并卟啉在DMSO中与TFA反应的质子化常数,并讨论了取代基对质子化反应的影响。结果表明,上述三种四环己烷并卟啉在与TFA反应时均一步得到两个质子,质子化反应常数(logβ2)分别为12.4(1)、12.0(2)和11.5(3)。

The UV-Vis spectra of 5,10,15,20-tatra（4-methylphenyl）tetrabutanoporphyrin（1）,5,10,15,20-tetraphenyltetrabutanoporphyrin（2）and 5,10,15,20-tetra（4-chlorophenyl）tetrabutanoporphyrin（3）were measured in dimethyl sulfoxide（DMSO）.As compared to those of the structural related porphyrins without the butano substituents,the absorption peaks of the tetrabutanoporphyrin were red-shifted by 19-33 nm.The absorption spectra of the three tetrabutanoporphyrins were also measured in trifluoroacetic acid（TFA）-DMSO and tetrabutylammonium hydroxide（TBAOH）-DMSO solutions and then compared to those of the same compounds measured in pure DMSO.The strong Soret band of the tetrabutanoporphyrin was red-shifted while the number of Q bands reduced in the TFA and TBAOH solutions,indicating that protonation or deprotonation reactions occurred between the tetrabutanoporphyrins and TFA or TBAOH.Protonation constant of each tetrabutanoporphyrin which reacts with TFA in DMSO was determined by micro spectral titration,and effect of the porphyrin substituents on the protonation reactions was discussed.The results indicate that the three examined tetrabutanoporphyrins can all accept two protons in a one-step reaction when react with TFA,and the protonation reaction constants（logβ2）are of 12.4 for compound（1）,12.0 for compound（2）and 11.5 for compound（3）,respectively.